Millimeter of mercury. A millimeter of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high and now defined as precisely 7002133322387415000â 133.322387415 pascals. It is denoted by the symbol mmHg. Although not an SI unit, the millimeter of mercury is still routinely used in medicine, meteorology, aviation, and many other scientific fields. One millimeter of mercury is approximately 1 torr, which is 1/760 of standard atmospheric ...
Vitrectomy is when the eye surgeon removes the vitreous from the inside of the eye. Pars plana vitrectomy is a general term for a group of operations on the deeper part of the eye, all of which involve the removal of some or all of the vitreous â the eyeâs clear internal jelly. Pars plana vitrectomy eye surgery is sometimes done to remove eye floaters or vitreous hemorrhage inside the eyeball. In a vitrectomy, the surgeon âvacuumsâ out the normally clear, jelly-like fluid that fills the inside of the eye, the vitreous humor, with a surgical instrument called a vitrector. The vitrectomy procedure
1 If a headache follows the flashes, it is called a migraine headache.. If these flashes or lines of light occur without a headache, it is called an ophthalmic migraine, or a migraine without a headache.  Posterior vitreous detachment - Posterior vitreous detachment (PVD) is a common condition usually caused by aging. The vitreous, which lies against the retina, is the jelly-like substance that fills the center of the eye. Made mostly of water, the vitreous fluid gives the eye its shape. As we get older, the composition of the vitreous changes, and becomes less firm. This change sometimes causes the vitreous to pull on the retina. If the force of the pulling becomes strong enough, the vitreous may actually separate from the retina. When this occurs, we see flashes of light or stars. Most of the time a PVD is annoying but harmless. However, about 5% of the time, a PVD can cause a retinal tear or detachment.